StevenJL

class Account < ActiveRecord::Base
  def withdraw(amount)
    # ...
  end
  
  def deposit(amount)
    # ...
  end
  
  def close!

StevenJL

class Account < ActiveRecord::Base
  def withdraw(amount)
    # ...
  end
  
  def deposit(amount)
    # ...
  end
  
  def close!

StevenJL

require "benchmark"

user = User.find_by_name("Teemo")

# See the time it takes to count the comments of a post in an n+1 query
puts Benchmark.realtime { user.posts.each { |post| puts post.comments.count } }

# See the time it takes to count the comments of a post with eager-loading
# Should be faster
puts Benchmark.realtime { user.includes(:posts).posts.each { |post| puts post.comments.count } }

StevenJL

http {

  # The `limit_req_zone` directive here prevents a single ip
  # address from making more than 30 requests per minute.
  # The `$binary_remote_addr` tells nginx to use the remote address
  # as the "key" for rate limiting.  The zone is used to define a
  # name and size where excessive requests are stored.
  limit_req_zone $binary_remote_addr zone=my_zone:12m rate=30r/m;
  
  location /do_not_dos_plz {

StevenJL

server {
  
  # Deny all ip addresses from range 192.168.1.0 - 192.168.1.255
  # since the /24 means the first 24 bits of the ip address (ie. 192.168.1)
  # is the network number, so deny all ips that belong to that network number.
  deny 192.168.1.0/24;
  allow all;


  location /admin {

StevenJL

# If there the upstream server errors, we want to with an error page.  
# Note the `location` directive here is performing a regex match.
location ~* (script1|script2|script3)\.php$ {
  proxy_pass http://192.168.0.1;
  
  # The `error_page` directive will return the document file
  # 50x.html depending on the upstream error.
  error_page 500 502 503 504 /50x.html;
}

StevenJL

location @proxy {
  # if an upstream server supports SSL, simply change the protocol
  # to https.
  proxy_pass https://192.168.0.1;
  
  # If the authenticity of the upstream server needs to be verified
  # then enable it using the `proxy_ssl_verify` directive.  This will
  # check the upstream server's certificate against certificate authorities
  # which are stored in /etc/ssl/certs
  proxy_ssl_verify on;

StevenJL

http {
  server {
  
    upstream upstream_server {
      server unix:/tmp/rails.sock;
    }
  
    # This defines a "named location" called @proxy, which can be
    # referenced elsewhere in this configuration.  It's sort of like
    # a variable for locations.

StevenJL

http {
  server {
    listen 80;
    server_name myreverseproxy.com;
    
    # The `upstream` directive defines an upstream server that can be referenced
    # in the rest of this file. In this case, it's a web application (ie. Rails/Rack) 
    # that is listening at the given unix socket.
    upstream upstream_server_name {
      server unix:/tmp/rack.sock;

StevenJL

# Every `http` block must contain at least one `server` block which
# defines http and/or https virtual hosts.
server {

  # Have a server listen to port 80, the standard HTTP port
  listen 80;
  
  # `server_name` creates a virtual host and sets its names
  server_name staticcontent.com;